Carbonic diesters are compounds of value as automotive gas additives and organic solvents or as reactants, replacing phosgene, in the production of various carbonates, carbamates, urethanes and fine chemicals such as drugs and agrochemicals.
For the commercial production of a carbonic diester, generally the corresponding alcohol is allowed to react with phosgene. However, this known technology demands the use of phosgene having a great toxic potential and, moreover, the reaction of the alcohol with phosgene gives rise to a large quantity of hydrochloric acid which is a highly corrosive substance.
Therefore, a technology has been proposed for producing a carbonic diester without the use of phosgene which comprises allowing the corresponding alcohol to react with carbon monoxide and oxygen in the presence of a catalyst. The catalyst used for this purpose can be classified into two major categories, i.e. the palladium catalyst including a compound of palladium as the main catalyst component and the copper catalyst including a compound of copper as the main catalyst component.
The liquid-phase reaction using the palladium catalyst is described in Japanese Patent Publication Nos. 8816/1986 and 43338/1986. According to this technology, a palladium compound as the main catalyst component is used in combination with a copper compound and an alkali metal compound. The liquid phase reaction conducted in the presence of a copper catalyst is described in Japanese Patent Publication No. 8020/1981. However, since the reaction system containing such a catalyst, irrespective of whether it is a palladium catalyst or a copper catalyst, is highly corrosive, the reaction must be conducted in a pressure-resistant reactor having an anticorrosive lining made of e.g. glass or a baked-on type enamel. Therefore, since there is an upper limit to the size of a pressure-resistant reactor having such an anticorrosive lining that can be fabricated, it is difficult to produce a carbonic diester containing such a catalyst on a commercial scale.
To obviate this corrosion problem associated with a liquid-phase reaction, a technology has been proposed for producing a carbonic diester which comprises allowing the corresponding alcohol to react with carbon monoxide and oxygen in a gas phase in the presence of a solid catalyst. For example, U.S. Pat. No. 4,625,044 discloses a catalyst comprising a complex formed with copper hydrocarbyloxy halide supported on an activated carbon for a reaction in a gas phase. JP-A-503460/1988 corresponding to WO87/07601 based on U.S. Ser. No. 871,725 (filed on Jun. 6, 1986) discloses a production process which comprises allowing all the reactants to react in a gas phase using a catalyst comprising metal halide supported on a solid support by an impregnation technique. In these literatures, an activated carbon especially an activated carbon derived from lignite, a kind of mineral substance, which have been acid washed is used in order to obtain a high reaction rate. Further, above-mentioned U.S. Pat. No. 4,625,044 teaches that a particularly preferred activated carbon is a Darco (trade name, ICI Americas, Inc.), as an acid washed activated carbon derived from lignite.
Further, G. L. Curnutt, who is the inventor of U.S. Pat. No. 4,625,044 and JP-A-503460/1988 mentioned above, reported in American Chemical Society concerning the catalytic activity in a gas-phase reaction in the presence of solid catalysts using activated carbon as a support, wherein lignite, bituminous coal, peat, petroleum coke and the like was used as the raw material of the activated carbon.
According to these technologies, however, a suffiient catalytic activity and selectivity of the reacion for the objective carbonic diester are not yet obtained, thus, production of the same in a good yield and with high selectivity has not been achieved.